In general, a paging receiver can be classified into one of four categories: an alert or tone only paging receiver, a numeric paging receiver, an alphanumeric paging receiver, or a voice paging receiver. One common characteristic of all of these paging receivers is that they monitor the air waves and notify the user when their particular address has been detected. For the alert or tone only paging receiver, the paging receiver would generate a tone or beep when its address is detected. The other paging receivers, upon detecting their address, would additionally store a message associated with the address signal and display or play it to the user. The message for a numeric paging receiver would be a set of numbers, typically the calling person's telephone number, and the message for an alphanumeric paging receiver would be a set of numbers and/or letters. The user of an alphanumeric paging receiver could therefore receive a message in the form of a telephone number with some descriptive text. For the voice paging receiver, the message that is stored is a voice message that the user can later play to hear the message.
A paging receiver is typically a rather small electronic device and, accordingly, has a limited amount of memory for storing messages that have been received from a base station in a paging system. Because of the relatively small size of the memory, the paging receiver can store only a limited number of messages. A user can delete messages from memory but will oftentimes desire to save a message, such as temporarily until the user makes a note of the message or until he or she is able to respond to the page. The messages that are saved in memory, however, reduce the space in memory that is available to receive new messages. This demand on space in memory is increasing as the size of the messages continue to grow and as users receive a greater number of messages. Although more memory can be added to accommodate more messages, the added cost and space needed for extra memory runs counter to the desires to keep the paging receiver small and inexpensive. A need therefore exists for a paging receiver which can display and/or play messages while efficiently using memory.
In addition to the demand on paging receiver memory, paging systems will be challenged as greater numbers of pages are being transmitted and as the size of the transmitted messages increases. Initially, when paging systems were only concerned with transmitting address signals of the paging receivers, the size of each transmission by the paging systems was relatively small. Paging receivers and paging systems, however, have undergone tremendous advances with paging systems now transmitting messages which can be hundreds of kilobytes or greater in size in addition to the address signals. Additionally, many paging receivers are actually paging transceivers which transmit acknowledgment signals back through the paging system. The capacity of the paging systems are therefore being challenged not only by messages of increasing sizes but also by reply signals transmitted from the paging transceivers to the paging system. The future of paging systems is therefore tied to the ability of the paging systems to control the number and size of the data transmissions and to provide additional features without sacrificing the quality of service to the user.
As discussed above, many paging transceivers are able to issue a reply or acknowledgment back to the base station in response to a received message. If the base station does not receive this reply or acknowledgment, then the base station assumes that the message has not been received and will repeatedly transmit the message until the reply or acknowledgment is received. Due to the high power levels at which the base station transmits its paging signals, the signals are usually easily received by all paging transceivers located within the coverage area of the base station antenna. The paging transceivers, on the other hand, must operate at lower power levels and often cannot transmit signals at sufficiently high levels to reach the base station. For example, when a paging transceiver is located in a basement of a building, in a subway, or in an airplane, the paging transceiver may be unable to issue a reply that can reach the base station. As a result, the base station may continue to transmit a page to a paging transceiver and the paging transceiver will continue to receive the message but the base station cannot detect the reply being issued by the paging transceiver. This unnecessary transmission of duplicate messages and the ineffectual reply signals transmitted by the paging transceivers consume valuable resources of the paging system and of the paging transceiver.
For safety reasons, a user may at times have to turn off his or her paging transceiver. For instance, when the user is on an airplane, the transmissions from the paging transceiver can interfere with the instrumentation or communication within the cockpit of the plane. The paging transceiver therefore should not be operating within the plane or around other electronic equipment that are sensitive to interference from the signals transmitted by the paging transceiver. As another example, if the user is in an environment that contains electronic detonators for explosive materials, the signals transmitted by the paging transceiver could possibly trigger an explosion. The user therefore must turn his or her paging transceiver off to ensure that it does not transmit any reply or acknowledgment signals in response to a received page. Although it may be dangerous for the pager transceivers to issue a reply signal in these situations, the signals transmitted by the base station may at times be safely received by the paging transceiver. Since the paging transceiver automatically issues a reply in response to a received message, the paging transceiver must nonetheless be turned off so as to not pose a risk to the user. During these times that the paging transceiver must be turned off, the user unfortunately is unable to receive any page or message. A need therefore exists for a paging transceiver that can notify a user of a message without automatically generating a reply message or acknowledgment to the base station.